1. Field of Invention
This invention relates to control methods and systems for controlling the upshifting of at least partially automated vehicular mechanical transmission systems. In particular, the present invention relates to shift control methods/systems for automated mechanical transmission wherein the probabilities of successfully completing a selected upshift are evaluated in view of existing vehicle operating conditions and only feasible shifts are initiated. More particularly, the present invention relates to a control for evaluating the probabilities of successfully completing an upshift in a semi-automated mechanical transmission system, including an engine brake and not including a non-manual clutch actuator, under existing vehicle conditions, first under unassisted engine decay and then under engine decay rates enhanced by increasingly powerful engine brake retardation.
2. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles, such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, transmission shaft speeds, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Such fully automatic change gear transmission systems include automated transmissions wherein pressurized fluid is utilized to frictionally engage one or more members to other members or to a ground to achieve a selected gear ratio as well as automated mechanical transmissions utilizing electronic, hydraulic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e., positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are hereby incorporated by reference.
Semi-automatic transmission systems utilizing electronic control units which sense engine fueling, throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior art. Examples of such semi-automatic mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated transmission system provides semi-automatic shift implementation for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means and/or a manually only controlled master clutch. This type of system usually has at least one mode of operation wherein the shifts to be semi-automatically implemented are automatically preselected and includes a control/display panel or console for operator selection of a ratio change or operation in the automatic preselection mode and indication of automatic preselection of upshifts, downshifts or shifts into neutral. An electronic control unit (ECU) is provided for receiving input signals indicative of transmission input and output shaft speeds and for processing same in accordance with predetermined logic rules to determine (i) if synchronous conditions exist, and (ii) in the automatic preselection mode, if an upshift or downshift from the currently engaged ratio is required and to issue command output signals to a transmission actuator for shifting the transmission in accordance with the command output signals. Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; and 5,089,965, the disclosures of which are hereby incorporated by reference.
While the above-described automatic and/or partial automatic shift implementation-type vehicular mechanical transmission systems are well suited for their intended applications, they are not totally satisfactory as they will occasionally initiate an attempted shift, which, due to vehicle operating conditions, cannot be completed. This especially was a concern for upshifts of these mechanical transmission systems not provided with an automated clutch actuator and/or an input shaft brake and thus have input shaft deceleration limited to the natural decay rate of the engine without the benefit of an input shaft brake or the like.
Engine brakes, usually called "engine compression brakes" or "exhaust brakes," are well known in the prior art and such devices (such as the well-known "Jake Brake") are commonly provided on heavy-duty vehicles. These devices are typically manually operated, may provide variable retardation by manual selection of one, two or three banks of cylinders operation, and are utilized to retard the vehicle and, in recent developments, to quickly retard engine/input shaft speed for more rapid synchronization during an upshift. Examples of vehicular automated mechanical transmission systems utilizing engine compression brakes may be seen by reference to U.S. Pat. Nos. 4,933,850; 5,255,650 and 5,042,327, the disclosures of which are incorporated herein by reference.
The present invention is applicable to the types of engine brakes discussed above and to other types of devices which may be used to selectively decelerate the rotational speed of an engine. The term "engine brake device" is intended to include all such devices.
Generally, engine compression brakes are effective to alter, usually hydraulically, the engine valve timing/porting so that a relatively large compressive force and resistance is provided to rotation of the engine. The prior art automated mechanical transmission systems of the type having manually operated engine brakes were not totally satisfactory, as engine brake-assisted upshifts tended to be somewhat harsh and abrupt.